A:2Ag2O △_ 4Ag+O2↑
B:Fe2O3+3CO 高温_ 2Fe+3CO2↑
C:Fe+CuSO4=FeSO4+Cu
D:MgC12 电解_ Mg+C12↑
已知:M=x3﹣3xy+2x+1,N=﹣3x+xy,求多项式3M+2N,并计算当x=﹣1,y= 15 时,3M+2N的值.
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